Technical Field
The present invention relates to a method for sterilizing microbial cells by treating microbial cells or cultures containing microbial cells with a polyethylene glycol-based nonionic surfactant to achieve substantially complete sterilization of the microbial cells while maintaining enzyme activity expressed in the microbial cells at a high level, and sterilized microbial cells produced therefrom.
More particularly, the present invention relates to a method for sterilizing microbial cells by treating microbial cells with a polyethylene glycol-based nonionic surfactant which can be used in foods, thereby enabling use of the sterilized microbial cells for food production, and a substance containing the sterilized microbial cells.
Background Art
Some processes for preparing foods may require the use of various enzymes produced by various microorganisms. Namely, an intended enzyme may be obtained from a microorganism and then used as a constitutional material for foods.
As such, in the event of employing microorganism cells in the process of food production, there are problems in that viable microorganism cells can be leaked and incorporated into products, thereby causing secondary microorganism contamination.
To resolve these problems, such leakage of microbial cells is generally minimized by reacting microorganisms having high stability in a closed system and fixing the used microbial cells. In recent years, however, the use of genetically engineered microorganisms has been rapidly increased for mass production of specific enzymes. When such genetically engineered microorganisms are used in the process of food production, a complete sterilization of the microorganism cells is required to ensure food safety.
Methods for completely sterilizing microorganism cells are largely classified into two methods, i.e., a method using physical means and a method using chemical means. Examples of the method using the physical means may include methods of performing heating, ultraviolet irradiation, electromagnetic wave irradiation, sterilization filtration, or the like. Examples of the method using the chemical means may include methods using phenols, alcohols, oxidants, heavy metal ions, sterilization gases, or the like.
Korean Patent No. 10-0501864 discloses one example of a method for sterilizing microbial cells using chemical means.
This publication discloses a method for sterilizing Rhodococcus, which is a recombinant bacteria, using a cationic or an amphoteric surfactant. This method improves sterilization efficiency of microbial cells using a cationic surfactant. However, this method has a problem caused by benzethonium chloride used as a cationic surfactant.
Benzethonium chloride has strong sterilizing power and is used in medicines for treating rhinitis and stomatitis, mouthwash, and the like. However, recent studies report that benzethonium chloride is considered a representative environmental hormone causing endocrine disruption and is quite noxious to the human body.
Accordingly, the above method can be only employed in a method for sterilizing microbial cells for industrial purposes without risk of being introduced to the human body in specific applications. In this regard, the above method is far from a method for sterilizing microbial cells, which can be used for food production as suggested in at least some embodiments of the present invention.
The foregoing discussions in this section are to provide general background information and do not constitute an admission of prior art.